In manufacturing processes of a semiconductor device, in order to form a micro circuit pattern on a substrate such as a semiconductor wafer, a FPD substrate or a substrate for a solar cell, a certain process such as an etching process or a film formation process is repetitively performed on the substrate. Such process is carried out by a plasma processing apparatus.
The plasma processing apparatus includes, by way of example, a depressurizable processing chamber capable of introducing therein a processing gas, and a mounting table is provided in the processing chamber. A susceptor to which a high frequency power is applied is provided on the mounting table, and a substrate is mounted on a substrate mounting portion formed on a substantially center of the susceptor. An electrostatic attraction portion is formed on the substrate mounting portion, and the substrate mounted on the substrate mounting portion is held by an electrostatic attraction force.
In this plasma processing apparatus, the processing gas is introduced into the processing chamber, and the high frequency power is applied to the susceptor. Further, plasma of the processing gas is generated on the substrate held by the substrate mounting portion, and a process such as an etching process or a film formation process is performed on the substrate. Here, in order to perform a uniform and favorable process at a periphery of the substrate as well as at a center thereof, a focus ring is provided so as to surround the substrate mounted on the substrate mounting portion.
When the focus ring is provided, the process quality at the periphery of the substrate is affected by a top surface electric potential of the focus ring. For this reason, there has been developed a technique capable of changing the top surface electric potential of the focus ring by providing a dielectric member between the focus ring and the susceptor (see Patent Documents 1 and 2). By way of example, Patent Document 1 describes a technique for changing the top surface electric potential of the focus ring by providing the dielectric member therebetween so as to change impedance between the focus ring and the susceptor.
Meanwhile, Patent Document 2 describes a technique for removing deposits (CF-based polymer or the like) adhering to a rear surface of the periphery of the substrate by positioning an inner periphery of the focus ring below the periphery of the substrate and by providing the dielectric member between the focus ring and the susceptor. By providing the dielectric member between the focus ring and the susceptor, the impedance therebetween is increased. As a result, the electric potential of the focus ring during a plasma process is decreased to a level of the plasma potential. As described above, an electric field due to a potential difference is generated between the substrate (susceptor) and the inner side of the focus ring during the plasma process by changing the top surface electric potential of the focus ring. Therefore, ions in the plasma are attracted and introduced toward the periphery of the substrate due to the effect of the electric field, so that the deposits adhering to the periphery of the substrate can be removed.
Patent Document 1: Japanese Patent Laid-open Publication No. 2003-519907
Patent Document 2: Japanese Patent Laid-open Publication No. 2005-277369
Meanwhile, a resistance of the substrate as a target object varies depending on a material or a surface structure of the substrate. Further, a distance between the focus ring and the susceptor is changed depending on a thickness of the substrate mounting portion, a thickness of the dielectric member, a shape of the susceptor, or the like. Hence, when the dielectric member is provided between the focus ring and the susceptor as described above, a current may easily flow from the substrate toward the focus ring depending on a type of substrate or the distance between the focus ring and the susceptor. Accordingly, there are problems that a voltage applied to the periphery of the substrate may become non-uniform, and the top surface electric potential of the focus ring may be decreased to a level lower than a desired potential. As a result, the top surface electric potential of the focus ring may become non-uniform depending on a type of substrate.
However, in the above-described conventional plasma processing apparatus, the dielectric member needs to be replaced with other one in order to change a dielectric constant between the focus ring and the susceptor. In this way, since the dielectric member needs to be replaced whenever a type of the substrate is changed, a throughput may be decreased.